Polyphyllin D inhibits proliferation of K562 on human leukemia cells by inducing apoptosis and differentiation

Abstract

Objective To investigate the inhibitory effect of polyphyllin D on the proliferation of human chronic myelogenous leukemia (CML) cell line K562 cells and its mechanism. Methods Methyl thiazolyl thiazolium (MTT) assay was used to evaluate the inhibition effect of polyphyllin D on the proliferation of K562 cells. Flow cytometry was used to determine the effect of polyphyllin D on the apoptosis of K562 cells. The related proteins were analyzed by Western blotting. Results The MTT assay showed that polyphyllin D obviously inhibited the growth of K562 cells. The hemi-inhibitory concentration (IC50) of 24 hours for the K562 cells was (0.8±0.1)μmol/L. Flow cytometric results demonstrated that polyphyllin D significantly induced apoptosis in a dose-dependent manner, and the apoptosis rates of 0, 0.4, 0.8, 1.2 μmol/L polyphyllin D were (1.73±0.33)%, (14.47±2.57)%, (24.10±3.52)%, (31.51±4.09)% after 24 hours, with a significant difference (F=58.231, P<0.001). Western blotting showed that polyphyllin D significantly down-regulated the expression of Bcl-2, and this was accompanied by up-regulation of Bax, decrease of the Bcl-2/Bax ratio, up-regulation of cytochrome c and activation of caspase-3. Otherwise, polyphyllin D obviously induced monocyte differentiation by increasing CD14 expression on the surface of K562 cells. Conclusion Polyphyllin D can significantly inhibit the proliferation of K562 cells, and the mechanism may be realized by inducing apoptosis and promoting monocyte differentiation. Key words: Leukemia; Apoptosis; Cell differentiation; Polyphyllin D